There are known fiber application machines, commonly known as fiber placement machines, for the application to a mold of a wide strip formed of a number of flat fibers, of the ribbon type, impregnated with resin, particularly carbon fibers impregnated with a thermosetting or thermoplastic resin. These machines include a system for displacing a fiber application head, said head comprising an application roller intended to come into contact against the mold to apply the strip and means for guiding the fibers onto said application roller, fiber storage means and fiber conveying means for conveying fibers from said storage means to the application head.
The conveying means are generally formed of a plurality of pulleys built onto the different axes of a gantry type displacement system. The storage means, formed of a fiber bobbin creel, are also built into the displacement system as close as possible to the placement head. These different built-in elements are cumbersome and heavy, and restrict the fiber application speed. These machines do not allow fibers to be placed in small dimension components or on some female molds because of the space requirement and the limited runs of the different axes.
PCT publication WO2006/092514 proposes using conveying means formed of flexible tubes connecting the storage means to the application head, each flexible tube being able to receive one fiber into its inner passage. The flexible tubes are anchored by their ends to the application head and to the storage means respectively by upstream and downstream anchoring means, and have sufficient length and flexibility not to restrict the movements of the head displacement system.
Flexible tubes of this kind form conveying means that are simple in design, do not take up much space and are of reduced cost, making it possible to obtain high movement speeds, to place remotely the displacement system storage means, to eliminate the motor-driven slack recovery systems for fiber bobbins, to isolate the fibers from the outside, to simplify the application head displacement system, and particularly to use a displacement system such as a multi-articulated arm of the six axis robot type. These flexible tubes are to advantage associated with a tension limiting system, described in detail in the aforementioned patent document, able to exert tensile stress on the fibers coming from the storage means thereby limiting the take-up tension of the fibers at the application roller.
These flexible tubes cannot however prevent the fibers from turning over during some robot displacements, because of excess bending of the flexible tubes and/or excess friction of the fibers in the flexible tubes.